Process for the manufacture of tubular l&#39;s



C. J. MARTIN April 13, 1954 PROCESS FOR THE MANUFACTURE OF TUBULAR ELLS2 Sheets-Sheet 1 Filed Aug. 31, 1946 Nil. 45

rllll mms\ INVENTOR C2 ma/ MART/N C. J. MARTIN April 13, 1954 2Sheets-Sheet 2 Filed Aug. 51, 1946 m m H NM 1 in M V. B a 0 M 5 I wwf/ wPatented Apr. 13, 1954 PROCESS FOR THE MANUFACTURE OF TUBULAR L S ClydeJ. Martin, Bradford, Pa., assignor to Dresser Industries, Inc.,Cleveland, Ohio, a corporation of Pennsylvania Application August 31,1946, Serial No. 694,324

The present invention relates to the manufacture of tubular L's, theterm L" being used generically to comprise not only ninety degree turns,but also turns of other angles, for example forty-five degree Us orreverse bends.

Many methods have been used for forming L's, among which are: bending ablank of pipe or tubing around an external mandrel to any desired angle;drawing the tubing over an internal mandrel having eccentric portions tosimultaneously bend and expand the tubing into the desired shape; usingvarious combinations of external dies and internal mandrels such asbending the blank by external dies while simultaneously moving internaldies within the blank; forcing a straight piece of tubing in an endwisedirection through an external die having a curved passageway; and usingan internal segmented mandrel to support and shape the interior of theblank while forming the exterior of the blank between opposed dies asdisclosed in my copending application Serial No. 593,931, filed May 15,1945, now Patent No. 2,528,315.

Among the disadvantages of the prior methods is the large amount ofpower required to form the blank into the desired shape. In the priormethods, the forming is done in presses which are of large size inproportion to the size of the L and are comparatively slow in operation.Another. disadvantage in the use of the prior methods is that the L maybe buckled, wrinkled or collapsed during the forming of the L.

The present invention aims to overcome the foregoing disadvantages byproviding an improved method of forming tubular Us. By this method ashort radius tubular L is formed from a straight blank of tubular stockin three steps or operations. In the first operation the straight blankof cylindrical stock is flattened to a blank of generically ellipticalcross section. The term ellipticaP' or "obrotund is used herein to meannot only true elliptical shapes, but also to include shapesapproximating a pure ellipse such as an oval shape, all having agenerally arcuate edge and in which one principal axis is longer thanany other axis. The first step may be performed, for example, by passingthe blank between opposed rollers of suitable cross section, by pressingthe blank between opposed flat surfaces. or preferably, by pressing theblank be tween opposed die sections cooperating to form a die cavitystraight in longitudinal section and elliptically shaped in crosssection. In the second operation the straight elliptically shaped blankis curved into an elliptically shaped L of the desired radius. This stepis performed by position- 3 Claims. (c .15s 4s ing a segmented mandrelof elliptical cross section in the elliptical blank and pressing theblank with the mandrel therein between opposed die sections havingcooperating die cavities corresponding in contour to the shape of thedesired L. In the third or finishing operation the elliptically shaped Lis formed into an L of circular cross section. This step may beperformed by passing the elliptically shaped L between opposed rollers,by pressing the L between opposed fiat surfaces, or preferably, bypressing the blank between opposed die sections having cooperating diecavities corresponding in shape to the desired L.

The methods in accordance with the invention are advantageous in thatbending of the L is accomplished more easily with less distortion of thewall section. Buckling or wrinkling is eliminated because of thecomparatively small differences in radius between the inner and outersurfaces of the elliptical blank as compared with the larger difierencesin radius between the inner and outer surfaces of a cylindrical blank.The L's produced by the present method are accurately formed and arefree of wrinkles, radius errors and other imperfections.

An object of the present invention is to provide a more economicalmethod of forming tubular Us The economy results from the reduced powerrequirements in the bending operation. This is of particular importancein forming US of short radius in which larger amounts of power arerequired than in the making of Us of longer radius.

Another object of the invention is to provide a method of forming Lswith lesser danger of buckling, wrinkling or collapsing of the blankduring the forming operation. This is particularly important in theforming of Us of short radius and having relatively thin walls. By themethod of the invention, the stresses on the blank during the bendingoperation are materially reduced.

A further object of the invention is to provide a method of formingtubular L's which is particularly advantageous in cold forming of the Land makes it possible to use cold forming in many instances where hotforming would otherwise be necessary. While the method of the inventionis particularly useful in this respect, it is not to be limited to coldforming, as in the forming of L's beyond certain limits in diameter orwall thickness, or in the forming of Us or certain materials, theheating of the blank maybe desirable.

Apparatus for carrying out the method in acoperating dies for bending anelliptical blank in accordance with the invention, a. blank being shownin position in the open die and a mandrel being shown in theblank.

Fig. 3 is a, view similar to Fig. 2 but showing the dies closed and theblank formed into an L.

Fig. 4 is a plan view of the mandrel, the sections of which are shownseparated for the sake of clarity. Fig. 5 is a cross section. throughthe mandrel taken along the line 5-5 of Fig. 4.

Fig. 6 is a cross section through the mandrel taken along the line 6-5of Fig. 4.

7 is a plan View of the two sections, of a finishing die laid side byside with the .die cavities of both sectionsfacing up. J

- Fig. 8 is. a cross sectional-vi w of the finishing dies in closedposition with the formed L therein, the section being taken along theline 8-% of Fig. '7.

Fig. 8a is a section like Fig. 8 but showing a modification,corresponding parts being designated by the same reference numbers asFig. 8 with the addition of 100. V

Fig; 9 is a side view and end view of a blank before forming.

Fig. 10 is a side View and end view of a blank after the first formingoperation in which the blank has been given an elliptical crosssectional shape.

Fig. 11 is a side view and end'view of a blank after it has been formedinto an elliptically shaped L of the desired curvature or radius.-

Fig. 12 is a side view and end view of an L of circular cross sectionafter it has been formedby the finishing operation. 5

7 Referring to the drawings there is shown in- Figure 1 across'sectional viewof an elliptical forming die -10 which is used toform a straight cylindrical blank l2 (Fig. 9) intoa straight blank ofelliptical cross section i3 (Fig. 10) which,- in turn, is formed'inbending dies 51 and 52 (Figs. 2 and3) into a'curved L [5 or ellipticalcross-section (Fig.1l). The elliptical L I5 is then formed in finishingdies it into an L of circular cross section I? (Fig. 12).

The ellipticalfonning die l0 (Fig. 1) comprisesa pair of cooperatingsections 29 and 2! having cooperating-die cavities 22 and 23 whichtogether form a cavity 25 having a contour which is straight along itslongitudinal axis and elliptically shaped in cross section. V V I Ithas'been foundpreferable inpracticing the method of the invention, toform the cavity of the forming die with a cross section in which theminor axis is fifty percent to seventy-five percent of the major axis,although these limits may vary depending upon the various possiblecombinations of wall thickness, diameter and material of the blank'andradius of the L; It is understood, however, that the elliptical formingdie it may not be necesary in all cases, it being possible to fornrtheelliptical blank l3 (Fig. 10) by applying the cross section of themembers is in the'line' 4 a force approximately perpendicular to thelongitudinal axis of the blank, such as by applying pressure to blank I2between flat opposed surfaces, or by passing the blank between opposedrollers of suitable cross section.

Figs. 2 through 6 illustrate apparatus which is utilized in performingthe second or bending operation in accordance with the invention.Referring to Fig. 2, there is shown a segmental mandrel ordie ofelliptical cross-section 56 in placewitliin'anelliptical blank l3 inposition between two opposed die sections 5! and 52 having -coope'r-ating die cavities which together form a cavity corresponding incontour to the dsired elliptical L. The upper die section it is provided on. its lowerfaoe with a die cavity 53 which is approximatelysemi-elliptical in cross-section and curved to the radiusof the desiredL. in longitudinal section. For convenience of manufacture, the diemaybe made up of a pluralityof parts removably secured to a base portion 55b means of bolts 56 or the like.

The lower die section 52 has a die cavityfid complementing the diecavity 53 to form a cavity corresponding in contour to the desiredelliptical L. The lower die section may also be made up oi'a pluralityof parts removably'secured to a base portion 5'! by means of bolts 58 orthe like.

The die sections may be moved together to form the blank by any suitablemeans such as a hy draulic press. The upper and lower die sectionscooperate with the segmental mandrel to form a curved L of ellipticalcross-section. V

The segmental mandrel 50 (Fig. 4)- which cooperates with theopposeddie-sections in formin'g the-blank to the desired shape comprisesa plurality'of sections which are pivoted relative to one another toform-an articulated structure. The mandrel conforms to the inner surfaceof the blank and 'afiords substantially continuous support throughoutthe portion acted upon by the die. The mandrel 50 comprises a pluralityof spaced end sections 62 and53 and an intermediate or central section64. The end sections are substantially straight and are elliptical incrosssection, asshown in'F'ig. 5, so that the mandrel will fit into theelliptical blank l3 snugly without binding The intermediate orcentralsection 6 3 is elliptical in central cross section, the outerportion being a cuate or curved longitudinally corresponding to thecurvature of the desired L while the inner-portion is straightlongitudinally. The section thus has a surface-of double curvature.erably split along an inclined plane indicated,

for example by the line 65 to facilitate removal from the L. The ends ofthe central section are cut off at an angle, thus forming l -shaped ends66 and 6! which are received in V-shaped recesses 68 and 69 in the endsections 62 and 63.

. In forming an elliptical blank intoan elliptical L with the apparatusshown in Figs. 2th'rough 6,

a straight blank [3 (Fig. 10) is positioned inthe cavity of theopposeddies and the-segmental mandrel 50 is positioned-in the blank, asshown in Fig. 2, so that the minor axis of the ellipse of of action ofthe dies. The die sections are then brought together by the press. 7 ofthe mandrel 50 permits itto bend as the blank is progressively formed bythe cooperation of V the forming die sections 5! and 52 and theelliptical'mand'rel 50, the mandrel affording studport to substantiallythe entire inner surface-oi the blank and corresponding-withthe-diesections The central section 84' is"p ref-' The articulation in theforming operation. The straight end sec tions of the mandrel maintainthe ends of the blank straight and thus a tubular L may be formed inaccordance with this method, having straight ends of any desired length.

After the blank has been formed into the elliptical L, as describedabove, the finishing die 16 (Figs. 7 and 8) is used for forming the L ofelliptical cross section into an L of circular cross section. The die isdivided into two halves or sections 36 and 31, which are similar butop-' posed to one another, the line of division being in the plane-ofthe longitudinal curvature of the formed blank or L. The cooperating diesections 3E5 and 31 have opposed die cavities 38 and 39 which togetherform a cavity corresponding in shape to the shapeof the completed L. Thecentral portion of each die cavity is arcuate or curved in alongitudinal direction, corresponding to the desired curvature of the Lwhile the end portions of each die cavity are straight, being tangentialto the curved central portion. Each of the dies is shown as made up of aplurality of parts or elements removably secured to base plates ii) andll, for. example by suitable screws 42 or other retaining means. Thestraight portions of the die cavities can be of any desired lengths.Means is provided for forcing the dies toward one another to operate onablank positioned in the die cavity. For this purpose the dies are shownprovided with suitable lugs GB for adjustably securing the dies to theplatens of a suitable press in proper alignment and operative positionrelative to one another.

In some instances, for example when forming Ls of particularly resilientmaterial, it may be found desirable to perform more work on the blank inthe finishing operation, in order to compensate for the amount the metalsprings back and thereby produce a more accurately formed L. This resultis accomplished as illustrated in Fig. So by making the cooperating diesection cavities 38 and 139 with an elliptical cross section, the minoraxis of the cross section of the die cavity being perpendicular to theminor axis of the cross section of the curved elliptical L prior to thefinishing operation.

In forming a tubular L with the apparatus shown in Figs. 1 to 8, astraight blank of tubular stock i2 is positioned in the ellipticalforming die Hi. It is preferred in the case of short Ls that the edgesbe precut with inclined ends, as shown in Fig. 9, as by using a blankwith an edge of the proper angle the finished L will have I square ends.Thus, there will be no material wasted in finishing the edges. Theproper angle for the edge of the straight blank may be determined byexperience, as it varies with different diameters, lengths and angles ofthe Us. If an inclined edged blank is used, it is positioned in theforming die so that the shortened side faces the top section of the die(Figure 1). Pres- Slll'G is then applied, forming the elliptically.

shaped blank 13. The segmental mandrel 50 is positioned in the blank andthe blank is placed between the bending dies 51 and 52. The blank ispositioned with its shortened side facing the die 55. Pressure is thenapplied forming the curved elliptical L IS. For some purposes the L maynow be considered a finished product. However, as it is generallyrequired that the L have a circular cross section, a further operationis necessary. The elliptically shaped curved L is is then positioned inthe finishing die l6 and the two sections of the die are moved towardone another in a direction transverse to the.

blank and approximately perpendicular to the plane of curvature. Thedirection of movement of the finishing diesrelative to the movement ofthe blank is thus approximately at right angles.

to the direction of movement of the elliptical forming die. Theoperationof the finishing dies changes the cross section of the curvedblank from an elliptical shape to a circular shape. While thelongitudinal curvature remains approximately the same, any slightdeviation is corrected.

While certain forms of apparatus for carrying out my invention have beendescribed, it will be understood that the invention is in no way lim-.

ited to this specific apparatus or to the particular steps described,but is subject to various modifications and variations. For instance, agreater number of dies may be employed, each set of dies performing aportion of the forming operation.

The method is equally applicable to tubular Ls, of circular or othercross section, and the straight.

tubular blank may be either square ended or provided with inclined endsas shown in Figure 9. Still other embodiments and variations of theinvention within the scope of the appended claims will be obvious topersons skilled in the art.

What Iclaim and desire to secure by Letters Patent is:

l. A method of forming a tubular L. of circular cross-section from astraight cylindrical blank, which comprises providing a cylindricalblank with an elliptical crossesectional shape, positioning in theelliptical blank an articulated mandrel of elliptical cross-section andhaving straight longitudinal end portions and a central portion havingan arcuate lower surface and. a substantially straight upper surface ina longitudinal porting the end portions and central portion of.

said elliptical blank both interiorly and exteriorly and therebymaintaining the elliptical cross-section, removing the blank frombetween said dies and removing said mandrel from the blank, placing theblank thus formed between dies having cooperating die cavitiescorresponding to the shape of the finished L and moving said dies towardone another to impart to said blank a substantially circularcross-section.

2. A method of forming a tubular L from a straight cylindrical blank,which comprises forming a straight blank with an ellipticalcrosssectional shape, pressing a central portion of one side wall ofsaid elliptical blank between a rigid die surface disposed inside theblank, said surface being convexly arcuate in a longitudinal directionand convexly semi-elliptical in cross-section and a mating rigid diesurface outside the blank, said outer die surface being concavelyarcuate in a longitudinal direction and concavely semi-elliptical incross-section, the pressure being exerted in a direction substantiallyperpendicular to the longitudinal axis of the elliptical blank andperpendicular to the major axis of the elliptical cross-section of theblank, the cross-sectional elliptical curvature of said inner and outerdie surfaces being substantially the same as the crosssectionalcurvature of the inner and outer surfaces respectively of saidelliptical blank, simultaneously pressing the opposite side wall of saidelliptical blank in the same direction between a rigid die surfaceinside the blank, said latter surfaces being substantially straight in alongitudinal direction and semi-elliptical in cross-section and anopposed rigid die surface outside the blank which is concavely arcuatein a longitudinal direction and concavely semi-elliptical incross-section and simultaneously pressing each end portion of saidelliptical blank between an inner rigid die surface which is rectilinearin a longitudinal direction and convexly elliptical in cross-section andopposed outer rigid die surfaces each of which is rectilinear in alongitudinal direction and concavely semi-elliptical in cross-sectionand thereafter pressing the blank thus formed between opposed rigid diesurfaces each. of which in an axial direction is arcuate with straightend portions and in cross-section is substantially semi-circular, thelast mentioned pressing being in a direction perpendicular to the minoraxis of the elliptical cross-section of said blank.

3. A method of making a tubular L from a straight cylindrical blank ofdeformable material having inherent resiliency, which comprises forminga straight blank with an elliptical crosssectional shape and with endsout on at symmetrically opposite anglesso that the end edges lieapproximately in planes which converge at a point on an extension of theminor axis of the central cross-section of said blank, the blank thushaving a longer side and a shorter side, pressing a central portion ofthe longer side of said elliptical blank. between a rigid die surfacedisposed inside the blank, saidsurface being convexly arcuate in alongitudinal direction and convexly semi-elliptical in cross-sectionand. a mating rigid die surface outside the blank, said outer diesurface being concavely arcuate in a longitudinal direction andconcavely semi-elliptical in.cross-section, the pressure being exertedin a direction substantially perpendicular to the longitudinal axis ofthe elliptical blank and perpendicular to the major axis of theelliptical cross-section of the blank, simultaneously pressing theshorter side of said elliptical blank in the same direction between arigid die surface inside the blank, said latter surface beingsubstantially straight in a longitudinal direction and semi-ellipticalin cross-section and an opposed rigid die surface outside the blankwhich is concavely arcuate in a longitudinal direction and concavelysemi-elliptical in cross-section and simultaneously pressing each endportion of said elliptical blank between an inner rigid die surfacewhich is rectilinear in a longitudinal direction and convexly ellipticalin cross-section and opposed outer rigid die surfaces each of which isrectilinear in a longitudinal direction and concavely semi-elliptical incross-section and thereafter pressing the blank thus formed betweenopposed rigid die surfaces each of which in an axial direction isarcuate with straight end portions and in cross-section issemi-elliptical with the minor axis of said semi-elliptical surfaceperpendicular to the minor axis of the elliptical cross-section of theblank, the last mentioned pressing being in a direction perpendicular tothe minor axis of the elliptical cross-section of said blank and beingcontinued slightly beyond the point at which the cross-section of theblank becomes circular so that due to the inherent resiliency of thematerial the blank springs back to circular cross-section when pressureis relieved.

teferences Cited in the file Of this patent UNITED STATES PATENTS NumberName Date 953,253 Brinkman Mar. 29, 1910 1,136,364 Powell Apr. 20, 19151,225,788 Dies May 1 1917 1,875,954 Taylor Sept. 6, 1932 1,888,837Schutt Nov. 22, 1 32 2,044,322 Oliver June 16, 1936 2,179,530 Townsendet al. Nov. 14, 1939 2,267,774 Wall Dec. 3 1941 2,336,611 Hill et alDec. 14, 1943 2,413,547 Davidson -1. Dec. 31, 1946 2,449,423 TimmonsSept. 4, 48 2,528,315 Martin Oct. 3 1950 FOREIGN PATENTS Number CountryDate 5,019 Great Britain 1 1 ,278 Great Britain Mar. 29, 1923 570,251Germany Feb. 13, 1933 469,004 Great Britain July 16, 1937

